Device and method for producing and sealing packagings produced from at least one heat sealable packaging material strip

ABSTRACT

A tubular bag-making machine for forming a flexible tube from a hot-sealable web of packaging material sealed longitudinally by means of a longitudinal seam sealing device and transversely by means of a transverse seam sealing device to produce individual tubular bag packages. To improve the transverse sealing seams, bores which can be made to communicate in alternation with a negative-pressure source or an overpressure source are embodied in the sealing jaws of the transverse seam sealing device in regions having a reduced number of layers of packaging material to enable a good heat transfer and a higher sealing pressure in the region of changes in the number of layers of packaging material of the transverse sealing seams.

PRIOR ART

[0001] The invention relates to an apparatus and a method for producing and closing packages, made from at least one hot-sealable web of packaging material, as generically defined by the preambles to the independent claims.

[0002] One apparatus having the characteristics of the preamble to claim 1 is already known from German Patent Disclosure DE 43 35 577 A1. In producing packages with the known kinds of apparatus, the problem arises that over the cross section of the flexible tube formed, there are regions with varying numbers of layers of packaging material. This can for instance be due to the fact that a previously formed longitudinal seam is wrapped around a wall of the bag, so that in the region of the longitudinal seam there are four layers of packaging material, while in the region immediately next to it there are only two layers of packaging material. It is also usual to fold the web of packaging materials inward in a V in the bottom and top regions, so that in these regions as well, there are four layers of packaging material. The presence of different numbers of layers of packaging material over the cross section of the packages is problematic because in forming the transverse seams, it must be assured that the packages later cut apart from the flexible tube of packaging material have adequate tightness. In conventional transverse seam sealing devices, a relatively high molding pressure and/or a relatively high temperature is typically employed, so that in all regions of the cross section of the flexible tube, sufficient heat and pressure will be transmitted to produce tight transverse seams. There are limits, however, to both transferring suitable quantities of heat and applying suitable sealing pressures, especially when critical packaging materials are used or for the sake of output.

[0003] To overcome these problems, it is therefore known from German Patent Disclosure DE 199 04 154 A1 to embody flexible sealing faces on a transverse seam sealing device, which conform to the packaging material as a function of the varying number of layers of packaging material.

[0004] An embodiment with a similar effect is proposed by German Utility Model DE-GM 94 13 035, in which a silicone inlay is provided in a sealing jaw of a transverse seam sealing device, and this inlay also conforms to the packaging material so as to achieve a better heat transfer.

ADVANTAGES OF THE INVENTION

[0005] The apparatus according to the invention for producing and closing packages made from at least one hot-sealable web of packaging material and having the definitive characteristics of claim 1 has the advantage that with a relatively simple structural embodiment, it makes tight transverse seams and at the same time a high output of the apparatus possible.

[0006] The invention makes use of the thought that for producing tight sealing seams, adequate warming of the packaging material must be assured, particularly in the regions of the transverse seam to be formed that have a reduced number of layers of packaging material. While when the two sealing jaws are pressed together, good heat transfer from the sealing jaws into the packaging material is assured in those regions with an increased number of layers of packaging material solely by the pressure of the sealing jaws, in the regions with a reduced number of layers of packaging material, the heat transfer is reduced in those regions with a reduced number of layers of packaging material, because of the reduced initial pressure of the sealing jaws against the packaging material. It is therefore proposed according to the invention that suction openings be provided in these latter regions, which openings pull the packaging material against the heated sealing jaw and thereby assure a high heat transfer.

[0007] Another preferred embodiment of the invention provides that the suction openings be made to communicate with a negative-pressure source. This makes it possible to press the layers of packaging material, after they warm up, against one another by means of the overpressure, so that a more-intimate contact between the warmed layers of packaging material and thus a tighter transverse seam can be formed.

DRAWING

[0008] One exemplary embodiment of the invention is shown in the drawing and will be described in further detail below. Shown are:

[0009]FIG. 1, an apparatus for producing bag packages, in simplified front view;

[0010]FIG. 2, a bag package, produced by the apparatus of FIG. 1, in perspective;

[0011]FIG. 3, a section taken in the plane III-III in FIG. 2, to illustrate the different numbers of layers of packaging material;

[0012]FIG. 4, a single sealing jaw according to the invention, in a simplified perspective view;

[0013]FIG. 5, a simplified section through a transverse seam sealing device of the invention; and

[0014]FIG. 6, a section through a portion of the transverse seam sealing device of FIG. 5 during the sealing operation.

DESCRIPTION OF THE EXEMPLARY EMBODIMENT

[0015] In FIG. 1, a tubular bag-making machine 10, known per se, is shown. The tubular bag-making machine 10 has a forming shoulder 11, which embraces a combined forming and filling tube 12. By means of the forming shoulder 11 and the forming and filling tube 12, a hot-sealable web of packaging material 13, which is drawn from a supply roll not shown and is delivered to the forming shoulder 11 via a feed roll 14, is shaped into a flexible tube 15.

[0016] Two vacuum prestretching belts 18, which serve to prestretch the flexible tube 15, are disposed facing one another on the forming and filling tube 12, below the forming shoulder 11. At the level of the vacuum prestretching belts 18, a longitudinal seam sealing device 20 is also disposed on the front side of the forming and filling tube 12; it welds the two peripheral regions of the web 13 of packaging material, placed one above the other by the forming shoulder 11, into a longitudinal sealing seam 4.

[0017] A raisable and lowerable transverse seam jaw housing 21 is located below the forming and filling tube 12 and has a folding device, not shown, for the flexible tube 15 as well as a sealing device 22, which includes two identically embodied heatable sealing jaws 23, 24 that can be moved toward one another and have an integrated cutting device.

[0018] By means of the tubular bag-making machine 10 described thus far and known per se, individual tubular bag packages 1, of the kind shown in FIG. 2, can be made. The tubular bag package 1 has a top closure 2, folded in finlike fashion, with a transverse sealing seam 3 and the longitudinal sealing seam 4, which extend over the entire front side 5 of the tubular bag package 1 and its top closure 2 as well as over the bottom region, not identified by reference numeral, of the tubular bag package 1. Because the top closure 2 has been folded with side folds 6 indented in a V and with the longitudinal sealing seam 4, the top closure 2 has a region 7 in which the packaging material is in two layers and another region 8 in which the packaging material is in four layers (FIG. 3). The likewise transversely sealed bottom region of the tubular bag package 1 also has regions with correspondingly different numbers of layers of packaging material.

[0019] The sealing jaws 23, 24 of the invention that are used to form the transverse sealing seams 3 will now be described in further detail in conjunction with FIGS. 4-7: In FIG. 4, one sealing jaw 23 is shown. It can be seen that the sealing jaw 23 has two sealing regions 26, 27; the upper sealing region 26 serves to form a transverse sealing seam 3, which is disposed in the bottom region of the tubular bag package 1, while the lower sealing region 27 serves to form a transverse sealing seam 3 disposed on the top closure 2 of the tubular bag package 1. A cutting knife 28, which cuts the individual tubular bag packages 1 apart from the flexible tube 15, can also be seen between the two sealing regions 26, 27.

[0020] Electrically operated heating cartridges, not shown, are disposed in the sealing jaw 23 and assure that the contact face 29 of the sealing jaw 23, oriented toward the flexible tube 15, will upon contact with the flexible tube 15 transmit sufficient heat into the regions of the flexible tube 15 that are to be sealed. For putting the sealing jaw 23 into contact with the flexible tube 15, the sealing jaw 23 is for instance coupled to a pneumatically operated drive mechanism 30, which is supported in the transverse seam jaw housing 21, and which assures a motion of the sealing jaw 23 in the direction of the double arrow 31.

[0021] A plurality of groups of bores 33, which are each coupled with a respective central conduit 34, 35 inside the sealing jaw 23, discharge into the contact faces 29, oriented toward the flexible tube 15, of the sealing jaws 23. The two conduits 34, 35 in turn discharge into a combined connection 36, which can be made to communicate with a negative-pressure source 37 or an overpressure source 38. The coupling of the combined connection 36 to the negative-pressure source 37 or the overpressure source 38 is effected by suitable triggering of valves 41, 42 by means of the control unit of the tubular bag-making machine 10.

[0022] An essential feature is the disposition of the bores 33 in the contact faces 29, which depends on the location and number of the different layers of packaging material, which will now be discussed with reference to FIG. 5. It can be seen from FIG. 5 that the bores 33 are disposed in those regions 7 in which there are only two layers of packaging material in the flexible tube 15, while no suction bores 33 are disposed in the regions 8 in which there are four layers of packaging material.

[0023] The function of the sealing device 22 and the sealing jaws 23, 24 will now be addressed, with reference to FIGS. 6 and 7: In FIGS. 6 and 7, in each case shown enlarged but not to scale, part of the cross section of the tubular bag package 1 is shown as a transverse seam 3 is being formed. For forming the transverse sealing seams 3, it is necessary that the two sealing jaws 23, 24 be moved toward one another by the drive mechanism 30, so that the contact faces 29 come into contact with the flexible tube 15. Since because the flexible tube 15 is in four layers in the regions 8 the sealing jaws 23, 24 do come into contact with the flexible tube 15 until in the regions 8, a greater quantity of heat is also first, and because of the greater pressure, transmitted from the contact faces 29 into the flexible tube 15 in the regions 8. To compensate for this effect, when the sealing jaws 23, 24 are brought into contact with the flexible tube 15, the negative-pressure source 37 is made to communicate operatively with the bores 33 via the one valve 41, so that via the bores 33, the flexible tube 15 in the two-layered regions 7 is drawn against the corresponding contact faces 29 (FIG. 6). Thus in the two-layered regions 7 of the flexible tube 15 as well, a good, that is enhanced, heat transfer from the contact faces 29 into the flexible tube 15 is assured.

[0024] After a certain period of time, the valve 41 is closed and the valve 42 is opened, so that now the bores 33 communicate with the overpressure source 38. The effect is that the two-layered regions 7 are additionally pressed together with compressed air, along with the sealing pressure applied by the sealing jaws 23, 24, in order to assure an especially intimate bond or welding of the flexible tube 15 within the regions 7. In other words, this means that the overpressure generates an additional pressure on the regions 7, so that the pressure in the regions 7 is as equal as possible as the pressure generated solely by the sealing jaws 23, 24 in the regions 8 (FIG. 7).

[0025] The entire welding operation, that is, the forming of the transverse sealing seams 3, takes place while the two sealing jaws 23, 24 are moving out of the position shown in FIG. 1 into their lower position shown in dot-dashed lines. After the welding or forming of the transverse sealing seams 3, the two sealing jaws 23, 24 move apart again during their upward motion, so that they can form the next transverse sealing seams 3.

[0026] It will additionally be noted that the sealing jaws 23, 24 described can be modified in manifold ways without departing from the concept of the invention, which is, in those regions where there is a reduced number of layers of packaging material, to assure a better heat transfer and an increased sealing pressure by using bores that communicate with a negative-pressure source or an overpressure source. For instance, it is conceivable for the bores 33 to be made to communicate with only a negative-pressure source or only an overpressure source, since both provisions by themselves already mean an improvement in the sealing quality. The number or disposition of the bores 33 in the sealing jaws 23, 24 can also be adapted to a particular intended application. 

1-4. (canceled)
 5. An apparatus (10) for producing and closing packages (1), made from at least one hot-sealable web of packaging material (13), the apparatus comprising a flexible-tube-forming device (11, 12) for forming a flexible tube (15) from the at least one flat web (13) of packaging material), a longitudinal seam sealing device (20) for forming a longitudinal seam (4) in the region of overlapping portions of the at least one web (13) of packaging material), a transverse seam sealing device (22), which includes two heatable sealing jaws (23, 24) that can be moved counter to one another in order to divide the flexible tube (15) into individual portions, defined by transverse seams (3), for the ensuing cutting apart of packages (1), at least one bore (33) in at least one of the sealing jaws (23, 24), on the side toward the flexible tube (15), a negative-pressure source (37); and means establishing communication between the at least one bore and the negative pressure source, the at least one bore (33) being disposed in a region (7) of the cross section of the transverse seam (3) to be formed, which region has a reduced number of layers of packaging material compared to other regions (8).
 6. The apparatus of claim 5, further comprising an over pressure source, and means establishing communication between the at least one bore (33) not only with the negative-pressure source (37) but in addition and in alternation with the overpressure source (38).
 7. A method for producing and closing packages (1) made from at least one hot-sealable web of packaging material (13), by means of an apparatus (10) defined by claim 4, the method comprising the steps of first shaping a flexible tube (15) from the at least one web (13) of packaging material, forming a longitudinal seam (4) and transverse seams (3) in the flexible tube, the transverse seams (3) separating the packages (1) from one another, the forming of the transverse seams (3) being effected by pressing together a sealing device (22) that includes the heatable sealing jaws (23, 24) to apply a pressure to the flexible tube (15) therebetween, establishing communication between the negative-pressure source (37) and the at least one bore (33) tp generate a negative pressure in at least one bore (33) of one sealing jaw (23, 24), to thereby press one region (7) of the flexible tube (15) in contact with the corresponding sealing jaw (23, 24), which region (7) has a cross section having a reduced number of layers of packaging material compared to other regions (8).
 8. The method defined in claim 7, further comprising the steps of providing an overpressure source (38), and establishing communication between the at least one bore (33) with not only the negative pressure source (37) but also and in alternation with the overpressure source (38). 